This disclosure relates generally to methods and apparatus for drilling wellbores. More specifically, this disclosure relates to methods and apparatus for increasing the diameter of a wellbore through reaming operations. Still more specifically, this disclosure relates to increasing the diameter of a wellbore without rotating the drill string.
In drilling a wellbore into the earth, such as for the recovery of hydrocarbons, a drill bit is connected onto the lower end of an assembly of drill pipe sections known as a drill string. The drill string is rotated so that the drill bit progresses downward into the earth to create the desired wellbore. In certain applications, such as the drilling of deviated or horizontal wellbores, the drill string is not rotated and downhole motors are used to rotate the drill bit. The downhole motors are often powered by pressurized drilling fluid pumped through the drill string. In addition to providing a conduit for the supply of pressurized fluid, the drill string may not rotate but can be used to transfer torque to lower end of the drill string, known as the bottom hole assembly, to help guide the path of the drill bit as it forms the wellbore.
During drilling, cuttings produced from the formation are carried away from the drill bit by the upward velocity of the drilling fluid. As the wellbore becomes more deviated from vertical, gravitational forces decrease the ability of the drilling fluid to carry cuttings out of the wellbore and the cuttings may settle along the bottom side of the wellbore. Settled cuttings, and the friction generated by the drill string contacting the bottom side of the wellbore can significantly increase the drag forces on the drill string.
In many drilling applications, the wellbore may need to be enlarged after it is initially drilled. This process is known as reaming. Reaming may be used to enlarge a section of the hole that was drilled too small, to open a section of wellbore, to remove an obstruction or dogleg from the wellbore, or any number of other operational reasons. Most conventional reamers are operated by rotating the drill string and therefore cannot be used in highly deviated wellbores or with systems that don't allow for rotating the drill string.
Thus, there is a continuing need in the art for methods and apparatus for methods and apparatus to enlarge a wellbore using a reamer.